Predictive factors can sometimes be confused with prognostic factors. While both types of information do assist in providing information on the likely progression of a patient's disease, the terms prognostic and predictive differ in the following ways:
Prognostic factors provide information on clinical outcomes at the time of cancer diagnosis, independent of therapy. They also provide information on growth, invasion, and metastatic potential.
Predictive factors provide information on the likelihood of response to a given therapy. Some markers can provide both predictive and prognostic value. For example, estrogen receptor (ER) testing in breast cancer can be used to both predict response to a specific hormone therapy and is a factor that correlates closely with favorable short-term prognosis.
The most commonly applied predictive testing methods that are used to identify various subtypes of human breast cancer are:
- Estrogen receptor (ER) by immunohistochemistry (IHC)
- Progesterone receptor (PR or PgR) by IHC
- Human epidermal growth receptor 2 (HER2 or HER2/neu) by IHC or HER2 amplification status by in situ hybridization (ISH), chromogenic in situ hybridization (CISH), or fluorescent in situ hybridization (FISH)
The results of these tests provide specific information, which is used to determine particular treatments.
